As you may remember, I’ve designed a universal platform for building retro-computers “Retrobyte”. I have successfully tested it by building the “Mikro-80” computer a few months ago and now I’m working on adapting my other retro-computer project “AGAT-7” to this platform. “AGAT-7” requires more functionality than “Retrobyte” has, so I’ve build an extension board for[…]

The computer “Mikro-80” was made in the Soviet Union in 1980 by a team of enthusiasts before in 1982, the magazine “Radio” began publishing its documentations and schematics. In a nutshell, this was the first accessible personal computer in the USSR; in that era, only single digits of people in the country had the ability[…]

In my previous post, I explained my idea of a modular platform for building modern replicas of retro-computers, of which the Rev.A has already been built and tested. In the process, I found a few things to improve: On the silkscreen, the diode D1 was shown incorrectly (the cathode points to the anode) The voltage[…]

During the time I worked on the “Agat-7” replica, I came across the need for constant changes and improvements; these resulted from either new ideas or troubleshooting. Some of these troubleshoots involve tinkering with the circuit board. Currently, I have four different revisions and modifications of PCB’s for “Agat”; this isn’t even the total amount,[…]

I’m about to finalise my Rev.0 of the modern replica of the retro-computer “AGAT-7”. The next step will be Rev.A design with fixed mistakes, improvements and some new ideas. In this post I’m going to summarise the Rev.0 experience and share with you with some ideas for Rev.A. At the moment the Rev.0 computer starts[…]

In my project of a modern replica of a retro computer “Agat-7” I needed to generate several different clocks. Some of them can be produced by the PLL built in FPGA, others are a simple division of the main clock. But there is another group of clock signals that are not as simple to get.[…]

Let’s go to the following part of the schematic. Today it is the CPU, the SRAM and the joysticks. Here it is: “Agat-7” has 96Kb of RAM, so we need 128Kb SRAM chip. We can use 128K x 8bit or 64K x 16bit chips. The second option requires 9 more FPGA pins to connect but[…]

At the moment I’ve completed the schematics and I’ve started to work on PCB layout. There are going to be some changes caused by discovered mistakes or better layout. So, please, treat it as a draft on this stage. Please, let me know if you notice any mistakes. Today we will have a look at[…]

I’ve spend some time to debug STM32L based 140K “floppy-drive” for my “Agat-7” replica project. It is already perfectly workable in read only mode. I transferred it to SPI interface to save some FPGA pins and now I need only 5 pins instead of 12. For 840K floppy drive it will save even more pins.[…]

HD44780-compartible LCD digital-alphabetical displays are very convenient to use in hobby projects. They exist in different sizes and are quite cheap. The most popular are 2 line modules with 16 characters per line (16×2). Also, 8х2, 16х1, 20х2, 20х4 and 40х2 modules exist. For my “AGAT-7” retro computer project I use 20×4 LCD module. Most[…]